In many states trailers with a gross vehicle weight rating of 1500 pounds or greater is required by law to have what equipment

For trailers with weights of 1500 pounds or greater, the law states that an independent brake system should be equipped for that trailer. They should be equipped with brakes which are sufficient to direct the movement of and to stop and hold such vehicle. Brakes shall also be designed and attached such in case of an accidental breakaway of the towed vehicle, the brakes shall automatically apply.

uses : -

1.aneroid barometers primarily measure whether pressure is rising or falling.

2.aneroid barometers are often used for reading pressure in homes and recreational boats.  

3.other uses may include barographs in meteorology and altimeters in modern aircraft.  

4.this type of barometer can announce whether a high or low pressure system is coming or whether it is becoming more intense.  

5.there are different types of aneroid barometers, such as the altimeter, which measures altitude, or distance above sea level.  

6.another example is a barograph, which is a modified aneroid barometer that provides constant readings of atmospheric pressure on graph paper.  

7.when used in this capacity, the aneroid barometer can store a week's worth of data.

android diameter a device for measuring atmospheric pressure , often specially calibrated for use as an altimeter ,consisting of a box or chamber partially exhaused of air, having an elastic top and a pointer to indicate the degree of compression of the top caused by the external air

refer to the attachment for the characteristics : -